As people's demands for wireless high-speed transmission increase, oscillating frequencies of radio frequency (RF) oscillators must be increased correspondingly. However, the increase of oscillating frequencies of RF oscillators also worsens the Inphase-Quadrature (I-Q) imbalance effect of the RF oscillators.
In wireless network communication systems, there is an amplitude imbalance and/or phase imbalance between the inphase channel and quadrature channel of the receiving end. As a result, image aliasing occurs in Orthogonal Frequency-Division Multiplexing (OFDM) systems, which affects the signal quality of the wireless communication system. Therefore, it is difficult for a wireless communication system without an I-Q imbalance compensation to provide desirable communication quality.
Conventional I-Q imbalance compensation methods may be generally divided into the following two categories: (1) performing detection and making compensation according to a time-domain or frequency-domain preamble signal or pilot signal that is already known; and (2) making compensation by using a time-domain filter. However, the former is known to have a high computational complexity, which tends to consume too many hardware resources. The latter is known to have a long latency, which tends to cause a long waiting time.
To compensate for the I-Q imbalance effect in modern wireless communication systems due to high-speed wireless transmission, Taiwan Invention Patent Application No. 101105226 (Publication No.:201336240 ), whose corresponding US application is U.S. patent application Ser. No. 13/443,281 (Publication No.:2013/0216004A1), has disclosed a receiver with an I-Q imbalance compensation and an I-Q imbalance compensation method thereof which features a low computational complexity and a short latency. However, the receiver and I-Q imbalance compensation method thereof disclosed in this Taiwan Invention Patent Application fail to take into account noises and low-pass filter (LPF) mismatches on the I-Q imbalance compensation.
Accordingly, it is important to provide a solution that takes into account noises and the LPF mismatches, presents a low computational complexity and a short latency, and can still effectively compensate for the I-Q imbalance effect in modern wireless communication systems due to high-speed wireless transmission.